MCQs on Dental Materials : Amalgams Part 2

# Advantage of zinc containing amalgam is :
A. Better handling property
B. Dimensional stability
C. Resistance to creep
D. Toxicity to pulp and dentin

# Cause of expansion in zinc containing amalgam is :
A. Zinc and water
B. Water
C. Hydrogen
D. Nascent oxygen

# What is the working time of amalgam ?
A. One to two minutes
B. Three to four minutes
C. Five to six minutes
D. Seven to eight minutes

# Which of the following amalgam alloys is least susceptible to creep ?
A. Lathe cut
B. Spherical
C. Microfine
D. Dispersion with high copper

# The percentage of copper in high copper alloy is :
A. 10-12%
B. 0-6%
C. 13-30%
D. 20-30%

# How soon after a moisture contamination does a zinc containing amalgam alloy start expanding ?
A. 24 hrs
B. 1-2 days
C. 3-5 days
D. 7 days

# What is common in amalgam and ceramics?
A. More compressive strength but less tensile strength
B. More compressive strength and tensile strength
C. Less compressive strength but more tensile strength
D. Less compressive strength and tensile strength

# What is the most frequeently used restorative material?
A. Silicate
B. Amalgam
C. Composite
D. Gold

# Which of the following constituents of amalgam alloy decreases expansion?
A. Copper
B. Zinc
C. Silver
D. Tin

# Which of the following silver amalgam alloys have the maximum strength ?
A. Lathe cut
B. Spherical
C. Admixed
D. Single composition

# The higher the Hg alloy ratio in dental amalgam:
A. Higher the strength
B. Lower the creep value
C. More matrix material formed
D. More gamma 1 phase formed

# Copper content in low copper amalgams is :
A. 6%
B. 12-30%
C. 29%
D. 19%

# Ag-Cu eutectic alloy has a characteristic property of that fusion temperature of :
A. the resultant alloy is greater
B. the resultant alloy is lesser
C. the resultant alloy varies according to the content of Ag and Cu
D. None

# Which phase provides maximum strength in hardened mercury/silver alloy ?
A. Silver/Mercury phase
B. Silver/Tin phase
C. Tin/Mercury phase
D. Zinc/Mercury phase

# Absorption of mercury in the human body occurs least from:
A. Lungs
B. Gastrointestinal tract
C. Skin
D. Kidneys

# The tarnished layer of silver amalgam consists of :
A. Sulphides of silver
B. Oxides of tin
C. Chlorides of tin
D. All of the above

# Which is not true about high copper amalgam alloys ?
A. Low tensile and compressive strength
B. Low Hg:alloy ratio
C. High tensile strength
D. Low creep

# The threshold limit value of mercury exposures is :
A. 0.01 mg/m3
B. 0.05 mg/m3
C. 0.1 mg/m3
D. 0.001 mg/m3

# "Amalgam" means :
A. A metallic powder composed of silver, tin, copper and zinc
B. An alloy of two or more metals, one of which is mercury
C. An alloy of two or more metals that have been dissolved in each other in the molten state
D. A metallic substance in powder or tablet form that is mixed with mercury

# Mercury intoxication in dental office mainly results from :
A. Direct contact with mercury
B. Inhalation of mercury vapours
C. Ingestion of mercury
D. None of the above

# In amalgam alloy, which of following acts as oxygen scavenger?
A. Cu
B. Zn
C. Pd
D. Ag

# Over-trituration of silver alloy and mercury:
A. reduces contraction
B. increases the strength of lathe-cut alloy but reduces the strength of spherical alloy amalgam
C. decreases creep
D. gives a dull and crumbly amalgam

# By increasing the percentage of which metal, the strength and hardness of amalgam increases?
A. Ag
B. Zn
C. Cu
D. Hg

# Mercury rich condition in a slow setting amalgam alloy system inn a restoration results in :
A. Accelerated corrosion
B. Fracture of the restoration
C. Marginal damage
D. All of the above

# Which of the following statements is true regarding lathe cut copper silver alloy ?
A. requires least amount of mercury
B. achieves high compressive strength at 1 hr.
C. has tensile strength, both at 15 minutes and 7 days is comparable to high copper, unicompositional alloys
D. has lower creep value

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